Here is some information to my little brothers who new to IT Profession. Did any one know exactly what a networking is ? types of network ? how network help us ?
A network is nothing more than two or more
computers connected to each
other
so that they can exchange information, such as:
- e-mail messages or documents,
- Share resources, such as disk storage or printers.
The
connection may be via electrical cables that carry electrical signals,
or
fiber-optic cables by using impulses of light. Wireless networks let
computers
communicate by using radio signals.
A
network, in addition to special hardware, also requires special software
to
enable communications. Network support is built into all major
operating
systems, including all current versions of Windows, Macintosh
operating
systems and Linux.
-
Client Computers
-
Server Computers
-
Network Interface Cards (NIC)
-
Cables
-
Hubs & Switches
-
Wireless Networks
-
Network Software
Client Computers
The
computers that end-users use to access the resources of the network.
8They
usually run a desktop version of Windows along with application
software
such as Microsoft Office. Sometimes referred to as
WORKSTATIONS.
Server Computers
Computers
that provide shared resources, such as disk storage and
printers,
as well as network services, such as e-mail and Internet access.
Server
computers typically run a specialized Network Operating System
(NOS)
such as Windows 2000 Server, NetWare, or Linux along with special
software
to provide network services.
For
example, a server may run Microsoft Exchange to provide e-mail
services
for the network, or it may run Apache Web Server so that the
computer
can serve Web pages.
Network Interface Cards (NIC)
A
card installed in a computer that enables the computer to communicate
over
a network. Almost all NICs implement a networking standard called
ETHERNET.
Every client and every server computer must have NIC (or
built-in
network port) in order to be a part of the network.
Cables
Computers
in a network are usually physically connected to each other
using
cable. The most commonly used cable today is called Twisted Pair,
also
known as 10BaseT. Another type of cable commonly used is Coaxial.
For
high-speed network connections, fiber-optic cable is used.
Hubs & Switches
Each
computer in a network is connected by cable to a device known as a
hub
or switch. The hub or switch in turn, connects to the rest of the
network.
Each hub or switch contains a certain number of ports, typically
8
or 16. Hubs and Switches can be connected to each other to build larger
networks.
Wireless Networks
In
many networks, cables and hubs are making way for wireless network
connections,
which enables computers to communicate via radio signals.
In
a wireless network, radio transmitters and receivers take the place of
cables.
Advantage:
Flexibility
Disadvantage:
It is inherently less secure than a cabled network.
Network Software
What
really makes a network work is software. Server computers typically
use
special Network Operating System (NOS) in order to function
efficiently.
Client computers need to have their network settings
configured
properly in order to access the network.
Why Networking?
Networks
are all about sharing. Specifically, networks are about sharing
three
things: INFORMATION, RESOURCES & APPLICATIONS.
Sharing
Information
Networks
allow users to share information in several different ways. The
most
common way of sharing information is to share individual files. In
addition
to sharing files, networks allow users to communicate with each
other
in various ways. Example: Messaging applications like Microsoft
Outlook.
Users can also hold online meetings over the network. 8With
inexpensive
Video Cameras and the right software, users can hold
videoconferences
over the network.
Sharing
Resources
Certain
computer resources, such as printers or hard drives, can be set up
so
that network users can share them. Providing users with access to a
shared
hard drive is the most common method of sharing files on a
network.
A
computer whose main purpose is to host shared hard drives is called a
File
Server. A network can be used to share an Internet connection.
Sharing
Application
Networking
businesses allow several users to work together on a single
business
application. 8For example: An accounting department may have
accounting
software that can be used from several computers at the same
time.
SERVERS & CLIENTS
Only
two kinds of computers are on a network: Servers & Clients. The
network
computer that contains the hard drive, printers and other
resources
that are shared with other network computers is called a Server.
Any
computer that’s not a server is called a Client.
Dedicated
Servers & Peers
In
some networks, a server computer is a server computer and nothing
else.
This server computer is dedicated solely to the task of providing
shared
resources, such as hard drives and printers, to be accessed by the
network
client computers. Such a server is referred to as a dedicated
server
because it can perform no other tasks besides network services. A
network
that relies on dedicated servers is sometimes called a
client/server
network.
Other
networks take an alternative approach, enabling any computer on
the
network to function as both a client and a server. Thus, any computer
can
share its printers and hard drives with other computers on the
network.
8While a computer is working as a server, you can still use that
same
computer for other functions such as word processing. This type of
network
is called a peer-to-peer network because all the computers are
thought
of as peers, or equals. Peer-to-peer networking features are built
into
all current versions of Windows since Windows 95. Hence you don’t
have
to buy any additional software to turn your computer into a server.
All
you have to do is to enable the Windows Server features.
The
network server features that are built into desktop versions of
Windows
(such as Windows XP) aren’t very efficient because these
versions
of Windows were not designed primarily to be network servers.
Hence
you should use a full-fledged Network Operating System, such as
Windows
2000 Server.
Network Categorization
Based
on the geographical size, its ownership, the distance it covers and
its
physical architecture, networks can be categorized as:
-
LAN: Local Area Network
-
MAN: Metropolitan Area Network
-
WAN: Wide Area Network
LAN
Computers
are relatively close together, such as within the same office or
building.
LAN can extend to several buildings on a campus – provided the
buildings
are close to each other.
WAN
A
network that spans a large geographical territory, such as an entire city,
region,
or even an entire country. WANs are typically used to connect two
or
more LANs that are relatively far apart.
MAN
A
network that that’s smaller than a typical WAN but larger than a LAN.
Typically,
a MAN connects two or more LANs within a same city but are far
enough
apart that the networks can’t be connected using a simple cable
or
wireless connection.
Network Topology
The
term network topology refers to the shape of how the computers and
other
network components are connected to
each
other. Several different types of network
topologies:
-
Bus Topology
-
Star Topology
-
Ring Topology
-
Mesh Topology
Two
Important Terms
NODE:
is a device that is connected to the network.
PACKET:
is a message that is sent over the network from one node to
another
node.
Bus Topology
In
this, the nodes are strung
together
in a line. Commonly used
for
LANs. Every node on the
network
can see every packet that
is
sent on the cable. If the cable in
a
bus network breaks, the network is effectively divided into two
networks.
Star Topology
Each
network node is connected to a
central
device called a hub or a
switch.
Also commonly used for LANs.
If
a cable in a star network breaks,
only
the node connected to that
cable
is isolated from the network.
The
other nodes can continue to
operate,
unless, the node that is
isolated
happens to be the File
Server.
Hub
& Switch
A
hub doesn’t know anything about the computers that are connected to
each
of its ports. A switch knows which computer is connected to each of
its
ports. Strictly speaking, only networks that use switches have a true
star
topology. If the network uses a hub, the network topology has the
physical
appearance of a star, but is actually a bus.
Ring Topology
Packets
are sent around the circle from
computer
to computer. Each computer looks
at
each packet to decide whether the packet
was
intended for it. If not, the packet is
passed
on to the next computer in the ring.
Years
ago, ring topologies were common in LANs, as two popular
networking
technologies used rings: ARCNET and Token Ring. ARCNET is
still
used for certain applications such as factory automation. Token Ring
is
a popular network technology for IBM mid-range computers.
Mesh Topology
Mesh
Topology has multiple connections between each of the nodes on the
network.
Advantage: If one cable breaks, the network can use an
alternative
route to deliver its packets. Mesh networks are not very
practicable
in LAN setting. Mesh networks are common for metropolitan
or
wide area networks. These networks use devices called routers to route packets
from network
to network. Routers
are usually arranged
to provide multiple
paths between
any two nodes.
The Downside of Networking
After
you hook your computer up to a network, it’s not a Personal
Computer
anymore. You are now part of a network of Computers. 8Two
disadvantages
of using a network: the loss of user independence and the
need
for network management.
Network Administration
At
least one person should be designated as the Network Manager (also
called
Network Administrator). He is responsible for making sure that the
network
doesn’t fall apart or get out of control.
Manager’s
Job
-
To make sure that plenty of space is available on the File
Server
-
To back up the File Server regularly
-
To allow new employees access the network
-
To solve basic problems that the users can’t themselves
solve
-
To call in an expert when something really bad happens
UNDERSTANDING
PROTOCOLS & STANDARDS
Understanding Protocols
Protocols
& Standards are what make networks work together. Protocols
make
it possible for the various components of a network to communicate
with
each other. Standards also make it possible for network components
manufactured
by different companies to work together.
A
protocol is a set of rules that enable effective communications to occur.
Computer
networks depend upon many different types of protocols, which
are
very rigidly defined, in order to work. Various protocols tend to be
used
together in matched sets called protocol suites.
The
two most popular protocol suites for networking are: TCP/IP
(Transmission
Control Protocol/ Internet Protocol) and IPX/SPX (Internet
Packet
Exchange/ Sequenced Packet Exchange). TCP/IP was originally
developed
for UNIX networks and is the protocol for the Internet. IPX/SPX
was
originally developed for NetWare networks and is still widely used for
Windows
networks. A third important protocol is Ethernet, a low-level
protocol
that’s used with both TCP/IP and IPX/SPX.
Understanding Standards
A
Standard is an agreed-upon definition of a protocol. Standards are
industry-wide
protocol definitions that are not tied to a particular
manufacturer.
Many organizations are involved in setting standards for
networking.
- ANSI: American National Standards Institute
- IEEE: Institute of Electrical & Electronics Engineers
- ISO: International Organization for Standardization
- IETF: Internet Engineering Task Force
- W3C: World Wide Web Consortium
OSI Reference Model
Open
Systems Interconnection Reference Model is a framework into which
the
various networking standards can fit. Open Systems Interconnection
Reference
Model is a standard of standards. The OSI Model breaks the
various
aspects of a computer network into seven distinct layers.
Layers
Functions
APPLICATION
File Transfer, e-mail, Remote login etc.
PRESENTATION
ASCII Text, Sound
SESSION
Establish/ Manage Connection
TRANSPORT
End-to-End Communication: TCP
NETWORK
Routing, Addressing: IP
DTA
LINK Two party communication: Ethernet
PHYSICAL
How to transmit signal: Coding
Ethernet Protocol
The
most popular set of protocols for the Physical and Data Link layers is
Ethernet.
The Ethernet is defined by the IEEE standard known as 802.3.
The
actual transmission speed of Ethernet is measured in Mbps.
Ethernet
comes in three different speed versions:
- Standard Ethernet - 10-Mbps
- Fast Ethernet – 100-Mbps
- Gigabit Ethernet – 1-Gbps (or 1000-Mbps)
TCP/IP Protocol Suite
The
TCP/IP, the protocol on which the Internet is built, is actually not a
single
protocol but rather an entire suite of related protocols. The TCP/IP
suite
is based on a four-layered model of networking that is similar to the
seven-layer
OSI Model.
TCP/IP Layers & Functions
APPLICATION
LAYER
TRANSPORT
LAYER
INTERNETWORK
LAYER
NETWORK
ACCESS LAYER
IPX/SPX Protocol Suite
Novell
originally developed the IPX/SPX suite in the 1980s for use with
their
NetWare Servers. 8IPX/SPX also works with all Microsoft Operating
Systems,
with OS/2, and even with Unix and Linux.
IPX
stands for Internet Package Exchange. It’s a Network layer protocol
that’s
analogous to IP. SPX stands for Sequenced Package Exchange. It’s a
Transport
layer protocol that’s analogous to TCP. Unlike TCP/IP, IPX/SPX
is
not a standard protocol established by a standards group, such as IEEE.
Instead,
IPX/SPX is a proprietary standard developed and owned by Novell.
Both
IPX and IPX/SPX are registered trademarks of Novell.
Other Protocols Worth Knowing About
NetBIOS:
Network Basic Input Output System
NetBEUI:
Network BIOS Extended User Interface
AppleTalk:
Apple Computers have their own suite of network
protocols
known as AppleTalk
SNA:
Systems Network Architecture is an IBM networking architecture
used
with Mainframe computers
UNDERSTANDING NETWORK HARDWARE
The
building blocks of networks are network hardware devices such as
servers,
adapter cards, cables, hubs, switches, routers, and so on.
Servers
Server
computers are the lifeblood of any network. Servers provide the
shared
resources that network users crave, such as file storage, databases,
e-mail,
Web services, and so on. For a home network or a small office
network
with only a few computers, you can get away with true peer-topeer
networking.
That’s where each client computer shares its resources
such
as file storage or printers, and a dedicated server computer is not
needed.
Some
general things to keep in mind when picking a server computer for
your
network:
- Scalability
- Reliability
- Availability
- Service and Support
Server
Form Factors
The
term Form Factor refers to the size, shape, and packaging of a
hardware
device. Server computers typically come in one of the three
form
factors:
- Tower Case
- Rack Mount
- Blade Servers
Network Interface Cards (NIC)
Every
computer on a network, both clients and servers, requires a network
interface
card (NIC) in order to access the network. A NIC is usually a
separate
adapter card that slides into one of the motherboard expansion
slots.
However, some motherboards have a built-in network interface, so a
separate
card isn’t required. Most NICs made today work with both 10Mbps
and
100Mbps UTP networks (that is, 10BaseT and 100BaseT) and are called
10/100
Cards.
Network Cable
We
can construct an Ethernet network by using one of two different types
of
cables:
- Coaxial Cable
- Twisted Pair Cable (UTP/ 10BaseT)
Hubs & Switches
The
biggest difference between using coaxial cable and twisted-pair cable
is
that when you use twisted-pair cable, you must also use a separate
device
called a hub. A switch is simply a more sophisticated type of hub.
Repeaters
A
Repeater is a device that gives your network signals a boost so that the
signals
can travel farther. You need a repeater when the total length of a
single
span of network cable is larger than the maximum allowed for the
cable
type:
Cable
Maximum Length
10Base2
(Coaxial) 185 metres
10/100BaseT
(Twisted Pair) 100 metres
1.3.6
Bridges
A
bridge is a device that connects two networks so that they act as if they
are
one network. Bridges are used to partition one large network into two
smaller
networks for performance reasons.
Routers
A
router is like a bridge, but with a key difference. Bridges are Data Link
layer
devices. A router is a Network layer device. A router is itself a node
on
the network, with its own MAC and IP addresses.
UNDERSTANDING NETWORK OPERATING SYSTEMS
All
network operating systems, from the simplest (such as Windows XP
Home
Edition) to the most complex (such as Windows Server 2003), must
provide
certain core functions.
Some
of the core NOS features are:
- Network Support
- File Sharing Services
- Multitasking
- Directory Services
- Security Services
Microsoft Server Operating System
Microsoft
currently supports three versions of flagship Server Operating
System:
- Windows NT Server
- Windows 2000 Server
- Windows Server 2003
Windows
NT4 Server
Windows
NT was a 32-bit processing, a huge step up from the 16-bit
processing
of earlier versions of Windows. Windows NT was the first
Microsoft
Operating System that was reliable enough to work as a network
server
on large networks. Version 4.0 was shipped in July 1996.
Windows
2000 Server
Windows
2000 Server is currently the most popular server Operating
System
from Microsoft. ØWindows 2000 Server, built on the strengths of
Windows
NT Server, is faster, easier to manage, more reliable, and easier
to
use for large and small networks alike.
Windows
2000 Server comes in three versions:
- Windows 2000 Server
- Windows 2000 Advanced Server
- Windows 2000 Datacenter Server
Windows
Server 2003
Microsoft
had just released a new version of Windows Server called
Windows
Server 2003. For several years prior to its release, this new
version
was called Windows .NET Server. Windows Server 2003 was built
on
Windows 2000 Server with added features.
Windows
Server 2003 comes in Four versions:
- Windows Server 2003, Standard Edition
- Windows Server 2003, Web Edition
- Windows Server 2003, Enterprise Edition
- Windows Server 2003, Datacenter Edition
Novell NetWare
NetWare
is one of the most popular network operating systems, especially
for
large networks. NetWare has an excellent reputation for reliability.
NetWare
released the first version of NetWare in 1983.
The
NetWare Versions are:
- Novell NetWare Version 3.x
- Novell NetWare Version 4.x
- Novell NetWare Version 3.x
- Novell NetWare Version 6
- Novell NetWare Version 6.5 (Released in 2003)
Other Server Operating Systems
Two
other Server choices are:
- Linux
- Apple Mac OS/X Server
Linux
is a free Operating System that is based on UNIX, a powerful
network
operating system often used on large networks. Today, Linux is a
full-featured
version of UNIX and can be an excellent choice as a Server
Operating
System.
For
Macintosh Networks, Apple offers a special network server Operating
System
known as Mac OS/X Server. Mac OS/X Server has all the features of
a
server operating system: file and printer sharing, Internet features, email,
and so on.
